[sdiy] P.S. troubleshooting help

[Bruce Duncan]

A simpler fix is to turn up the current limit using the two trim pots 
on the power one main board.
This will often overcome the capacitive load issues. There is also a 
fix to increase one of the caps on the PSU board so current limiting 
sense doesn't trip
from inrush current on startup. I will have to look this up. Also I 
recommend replacing the transformer with a toroid to eliminate transformer hum.
Power ones are mechanically noisy especially when they get a bit on in years.
Hammond make a a nice 80VA 30V CT that works like a charm.

Bruce






At 02:07 PM 04/04/2009, you wrote:
> > turned it on a few hours ago and the negative side was below 1V...
>
>Is this with a load?
>
>If so, you should know that dual output Power One supplies will 
>sometimes latch up if the load is too capacitive. Typically, one 
>rail will come up but the other doesn't. Normally, the negative one 
>will not fire up since the positive rail takes more current.
>
>The latching up is likely to happen in modular synths because each 
>module may have a reasonable decoupling capacitance which then adds 
>up when all the modules are in place.
>
>Sometimes the supply will power up OK, sometimes not. The best thing 
>to do in this case is to reduce the amount of decoupling capacitance 
>on each of the modules. I reckon a max of 2uF to 3uF per module per 
>rail and you should be fine.
>
>The other option is to use time controlled power distribution. I 
>think Ken Stone makes a board that does this.
>
>And another option is to modify the Power One to have traditional 
>current limit rather than the usual current foldback method it 
>normally uses. I have done this on a couple of occasions and it works well.
>
>Tony
>
>www.oakleysound.com
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